In Grow a Garden, Pet Mutations give pets unique abilities, stat boosts, or visual changes.
You can mutate a pet that is level 50 and above by submitting it to the Pet Mutations machine.
Pet Mutations offer different passives like XP boosts, applying fruit mutations, and more.
The chances of obtaining each mutation differ, with rarer ones having a less than 1% chance.
This article contains a Rainbow Pet Mutation wiki in Grow a Garden, including its ability, boost type, boost amount, and chance.
Grow a Garden Rainbow Pet Mutation

Provides a bigger increase to the pet’s passive!
Passive Boost
+20%
3.22%
The Rainbow Pet mutation in Grow a Garden emits rainbow particles from a pet.
It provides a bigger increase to the pet’s passive.
Its boost type is a passive boost, and its boost amount is +20%.
The chance of obtaining it from the Pet Mutations machine is 3.22%.
Further reading
Grow a Garden Shocked Pet Mutation Wiki